Since 1930-1940 data on the lead bullets armour-piercing effect and on a high efficiency of metal explosion products have been published. The experimental data of that time were obtained by shooting the light lead bullet that blasted an armour of 12,8 mm thickness at a velocity of 1700 m/с. It is not known exactly till nowadays whether the armour-piercing effect will occur at lower velocities. The paper reveals that the armour-piercing effect of a medium hard plate with a 35 mm thickness occurs at lower bullet velocities ν = 667-760 m/s. This value is close to the theoretically predicted velocity which is equal to ν_cr = 702 m/s.